Method of inserting a fusible safety plug into a pressurized container



Jan. 9, 1968 G. R. WILLIAMS 3,362,063

METHOD OF INSERTING A FUSIBLE SAFETY PLUG INTO A PRESSURIZED CONTAINER Filed Jan. 23, 1964 I N VEN TOR.

ALJ M United States Patent 3,362,063 METHOD OF INSERTING A FUSIBLE SAFE Y PLUG INTO A PRESSURIZED CONTAHVER T Gladney R. Williams, 502 Main St., East Aurora, N.Y. 14052 Filed Jan. 23, 1964, Ser. No. 339,724 6 Claims. (Cl. 29-530) This invention relates to improvements in pressurized contarners and to methods of providing same.

It is known in the manufacture of pressurized contamers, such as aerosol containers, to provide a safety means therein whereby pressure within the container may be released upon it reaching a predetermined safe level. Thus, fusible plugs are provided on the container body whereby upon a certain temperature being reached and consequently upon a certain pressure being reached, the plug will melt, thus releasing the internal pressure and preventing the container from exploding.

Various attempts have heretofore been proposed which have as an important object, the provision of a simple means for installing the fusible plug onto the container body. Such means as have been proposed, employ the use of a separate plug which is inserted into a hole as defined by the container side wall or end cap. It will be appreciated that the provision of extra parts onto the container body during manufacturing increases the cost of the container and for this reason are not often employed.

Thus, in most cases, the containers are merely marked with a warning against overheating and a warning is also posted on the container against incineration upon the contents being used. It will be appreciated that large quantities of these spent containers are discarded daily and in areas where incineration is used to eliminate garbage, the containers must be fractured separately before incineration in order to prevent any explosion in the incinerator.

The problem of exploding containers is further magnified when one considers that in some cases exposure to sunlight may cause a pressurized container to rupture. Therefore, any safety means incorporated into the container must allow a gradual escape of dangerously compressed gas therewithin since the sudden release in pressure in a container which was stored on a shelf or the like would have the same effect as an explosion due to a rupture of the container. For this reason, any vent holes released by a fusible plug must necessarily be quite small in diameter in order to control the rate of pressure release.

A problem arises from the necessity of providing small diameter holes in the container since normal methods of providing holes, that is punches and the like, must be carefully applied since any variation beyond a predetermined limit in the diameter of the holes would seriously effect the rate of pressure discharge.

A further problem arises from the fact that the fusible plug normally provided in the holes in the container must be kept within certain narrow limits whereby the strength and softening point of the plug will be uniform. Thus, in general when providing fusible plugs in a pressurized container, the hole diameter as well as the plug size must be kept within narrow limits in order to ensure that the safety plug will operate satisfactorily under all expected conditions.

Accordingly, it is an object of the present invention to provide a pressurized container which incorporates a fusible safety plug therein having a high degree of reliability.

It is a further object of this invention to provide a method of incorporating a fusible safety plug in a pressurized container which may be applied directly into the manufacturing process of the container, and which will produce a safety plug of uniform quality and reliability.

It is a further object of this invention to provide a method of incorporating a fusible safety plug onto a pressurlzed container during the manufacturing thereof without serious alterations to the present manufacturing methods and to a method which may be applied to a variety of different forms of pressurized containers.

These and other objects and features of the invention will be apparent from the following detailed description and accompanying drawings in which like numerals refer to like parts.

In the drawings:

FIG. 1 is a schematic view of a manufacturing line for producing a container'according to the present invention;

FIG. 2 is a schematic section through a portion of the production line as illustrated in FIG. 1 and particularly illustrates the means for providing a fusible plug within the container;

FIG. 3 is an enlarged section of the present method for forming a hole through the container;

FIG. 4 is an enlarged section of the container wall and illustrates the fusible plug in place in the hole through said wall;

FIG. 5 is a section through a portion of the production line and illustrates a further embodiment of the present method;

FIG. 6 is an elevation view of one common form of pressurized container and illustrates one arrangement of fusible safety plugs thereon;

Having reference to FIG. 1, a production line for a pressurized container is illustrated diagrammatically and comprises a roll of strip like material 11 which is fed to a blank forming device 12 which severs the strip 11 into blanks of predetermined size, whereafter the blanks are fed into the roll forming device indicated as 13 to become cylinders 14. The cylinders 14 are then passed beneath a capping machine indicated as 15 and the completed cans are indicated at 16. It will be seen that this is the conventional method of producing pressurized containers, the drawing indicating in a simple manner the various steps employed in forming these containers.

The hole forming and plug forming portions of the present invention indicated generally as 17 in FIG. 1 are illustrated in more detail in FIG. 2 where a hole forming device indicated generally as 18 and a plug forming device indicated generally as 19 are illustrated. The strip of material 20 which is either a continuous strip or a strip which has been cut into lengths ready for forming the sidewalls of this container is set in from one side of the apparatus 17 where first is encountered the hole forming device 13.

The hole forming device indicated as 18 comprises a set of electrodes 21 above the strip 20 and a set of electrodes 22 below strip 20. By pairing the diameter of the electrodes 23 and 24 on sets 21 and 22 respectively and by suitably adjusting the voltage applied across the electrodes, a spark discharge therebetween will pierce a hole through the strip 20 of the required diameter.

Referring to FIG. 3, an enlarged section of the strip 20 is illustrated and shows the electrodes 23 and 24 spaced above and below the strip 20. It is expected that the diameter of the hole 25 shall be between to of an inch in diameter whereby upon a dangerous pressure increase within a container the pressure therewithin may be released controllably through the small diameter hole. Referring further to FIG. 3, it will be seen that strip 20 is provided with a film 26 thereon, the film 26 being applied prior to the strip 20 entering the hole piercing device 18.

In one preferred embodiment the strip 20 is made from aluminum or an aluminum alloy, whereby an oxide film 26 is provided thereon. It is Well known that new aluminum very quickly tarnishes to produce a dense, hard oxide film thereon so that even freshly rolled aluminum strip would have an oxide film which would form even during the rolling operation. For this reason it is considered by the present invention preferable to use aluminum or one of its alloys as the material for manufacturing the container, however, it will be understood that other materials may be resorted to and the film 26 may be applied in the form of a solution, which will thereafter harden onto the strip 20 to provide the necessary film.

Referring to FIG. 2 and FIG. 4, a fusible plug 27 is provided within the hole 25, the material of plug 27 adhering to the sides of the hole 25, the film 25 preventing the formation of any plug material other than in the hole 27.

Referring to FIG. 2, the method of applying the plug 27 is illustrated wherein a bath of molten fusible plug material 28 is provided together with a plurality of rollers 29 which forces the strip 20 down into the bath 28, Whereby in an action similar to soldering, the molten bath 28 fills into the hole 25 in the strip 20, the film 26 preventing the molten material 28 from adhering to any other portions of the strip 20. Thus, in each case the hole 25 accurately formed by a controlled discharge between the electrodes 23 and 24 is filled by the plug 27 in a highly accurate manner whereby a fusible plug of uniform reliability is retained.

Referring to FIG. 5, a method of applying an artificial film on the strip 20 is illustrated and comprises a bath 30 containing a film forming material 31. The roller 32 aids in driving the strip 20 down into the bath 30 where the material receives the necessary resistant film. It will be understood that the resistant film as applied to the strip 20 may be in the form of a liquid which will thereafter harden onto the strip or may be an oxidizing gas whereby the strip 20 is provided with an artificially applied oxide film, the requirement of the film being to prevent the adhesion of molten fusible material thereto during the plug forming operation within the device 19.

Referring to FIG. 6, a pressurized container such as an aerosol can indicated generally as 33 is illustrated and comprises a side wall 34 having a top in cap 35 and a bottom in cap 36 applied thereto. A preferred arrangement of fusible plugs is illustrated and comprises the pair of plugs 37 and 38 at one end of the wall 30 toward the top in cap 35 and a second pair of fusible plugs 39 (only one shown) located on the sidewall 34 towards the bottom in cap 36. In the drawing only one plug 39 is shown since the other plug 39 is diametrically opposite thereto. It will be seen from this arrangement that both sides and both ends of the container 33 are provided with a fusible plug whereby, upon heat being applied locally to some portion of the container 33, a fusible plug will be in position to sense the heat rise and thus provide the necessary safety features by melting.

From the foregoing it will be seen that the invention achieves the various objects and features by applying a method of incorporating fusible safety plugs in a pressurized container which ensures safety plu-gs having uniform features and at the same time provides a method of forming such plugs which can readily be incorporated into the existing production line for such pressurized containers as aerosol cans.

In use it will also be seen that the hole forming device 18 may be installed in the production line and that the plug forming device 19 may be installed thereafter, whereby, upon the holes being formed in the strip 20, the plugs may then be immediately formed within the holes, thus preventing the formation of oxide films on the sides of the holes which would otherwise tend to prevent the adhesion of the fusible material 28 therein. As an aid in preventing such oxide films from forming, a cover 40 may be placed over the devices 18 and 19 and an atmosphere of inert gas may be provided within the cover 40 whereby all oxidizing gases and fumes may be excluded during the hole forming operation and the subsequent filling of the hole with the fusible plug material. Now openings 41 and 42 may be provided beneath the cover 4'9 whereby the strip 20 may pass thereunder and an overpressure within the cover may be provided whereby a small leak rate of the inert atmosphere is allowed to escape from the openings 41 and 42 thus preventing the entrance of gas or vapour which may tend to oxidize the bare metal about the holes 25.

It will he also understood that although specific embodiments of the invention have herein been described and illustrated, the invention also contemplates such variations in design as may fall within the scope of the appended claims.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of incorporating fusible safety plugs in pressurized containers during manufacturing thereof from metal-lic strip material and comprising the steps of applying a resistant film to both sides of said metallic strip at least in the areas to be pierced; electro-piercing said metallic strip to form a plurality of holes therethrough in a predetermined pattern, thereby to provide said holes free from said resistant film; and applying fusible material having a melting point lower than said metallic strip to said pierced metallic strip, whereby said fusible material will adhere to said metallic strip in said holes thereby filling said holes, said resistant film preventing adhesion of said fusible material to said metallic strip beyond said holes, said filled holes thereby constituting said fusible safety plugs.

2. A method of incorporating fusible safety plugs in pressurized containers during manufacturing thereof from metallic strip material and comprising the steps of applying a resistant film to both sides of said metallic strip at least in the areas to be pierced; severing said metallic strip to provide a plurality of container blanks; electropiercing said metallic strip in an inert atmosphere to form a plurality of holes therethrough in a predetermined pattern, thereby to provide said holes free from said resistant film; and applying fusible material having a melting point lower than said metallic strip to said pierced metallic strip, whereby said fusible material will adhere to said metallic strip in said holes thereby filling said holes, said resistant film preventing adhesion of said fusible material to said metallic strip beyond said holes, said filled holes thereby constituting said fusible safety plugs.

3. A method of incorporating fusible safety plugs in pressurized containers during manufacturing thereof from metallic strip material and comprising the steps of forming an oxide film on both sides of said metallic strip at least in the areas to be pierced; electro-piercing said metallic strip in an inert atmosphere to form a plurality of holes therethrough in a predetermined pattern, thereby to provide said holes free from said oxide film; maintaining said pierced metallic strip in an inert atmosphere to prevent formation of an oxide film within said holes; and applying fusible material having a melting point lower than said metallic strip to said pierced metallic strip, whereby said fusible material will adhere to said metallic strip in said holes thereby filling said holes, said oxide film preventing adhesion of said fusible material to said metallic strip beyond said holes, said filled holes thereby constituting said fusible safety plugs.

4. A method of incorporating fusible safety plugs in pressurized containers during the manufacturing thereof from metallic strip material having an oxide film on both sides at least in the areas to be pierced and comprising the steps of electro-piercing said metallic strip in an inert atmosphere to form a plurality of holes therethrough in a predetermined pattern, thereby to provide said holes free from said film; and applying fusible material having a melting point lower than said metallic strip to said pierced metallic strip, whereby said fusible material will adhere to said metallic strip in said holes thereby filling said holes, said oxide film preventing adhesion to said metallic strip beyond said holes, said filled holes thereby constituting said fusible safety plugs.

5. A method of incorporating fusible safety plugs in pressurized containers during the manufacturing thereof from metallic strip material having an oxide film on both sides at least in the areas to be pierced and comprising the steps of electro-piercing said metallic strip in an inert atmosphere to form a plurality of holes therethrough in a predetermined pattern, thereby to provide said holes free from said oxide film; maintaining said pierced metallic strip in an inert atmosphere to prevent formation of an oxide film Within said holes; and applying fusible material having a melting point lower than said metallic strip to said pierced metallic strip, whereby said fusible material will adhere to said metallic strip in said holes thereby filling said holes, said oxide film preventing adhesion to said metallic strip beyond said holes, said filled holes thereby constituting said fusible safety plugs.

6. A method of incorporating fusible safety plugs in presurized containers during the manufacturing thereof from metallic strip material having an oxide film on both sides at least in the areas to be pierced and comprising the steps of severing said metallic strip to provide a plurality of container blanks; electro-piercing said metallic strip in an inert atmosphere to form a plurality of holes therethrough in a predetermined pattern, thereby to provide said holes free from said oxide film; maintaining said pierced metallic strip in an inert atmosphere to prevent formation of an oxide film within said holes; and applying fusible material having a melting point lower than said metallic strip to said pierced metallic strip, whereby said fusible material will adhere to said strip in said holes thereby filling said holes, said oxide film pre venting adhesion of said fusible material to said metallic strip beyond said holes, said filled holes thereby constituting said fusible safety plugs.

References Cited UNITED STATES PATENTS 2,171,588 9/1939 McGuifey 220-89 2,743,841 5/1956 Bugel 220-89 2,730,455 5/1956 Swann 1174 2,859,150 11/1958 Toulmin 117-4 JOHN F. CAMPBELL, Primary Examiner.

25 THERON E. CONDON, CHARLIE T. MOON 

1. A METHOD OF INCORPORATING FUSIBLE SAFETY PLUGS IN PRESSURIZED CONTAINERS DURING MANUFACTURING THEREOF FROM METALLIC STRIP MATERIAL AND COMPRISING THE STEPS OF APPLYING A RESISTANT FILM TO BOTH SIDES OF SAID METALLIC STRIP AT LEAST IN THE AREAS TO BE PIERCED; ELECTRO-PIERCING SAID METALLIC STRIP TO FORM A PLURALITY OF HOLES THERETHROUGH IN A PREDETERMINED PATTERN, THEREBY TO PROVIDE SAID HOLES FREE FROM SAID RESISTANT FILM; AND APPLYING FUSIBLE MATERIAL HAVING A MELTING POINT LOWER THAN SAID METALLIC STRIP TO SAID PIERCED METALLIC STRIP, WHEREBY SAID FUSIBLE MATERIAL WILL ADHERE TO SAID METALLIC STRIP IN SAID HOLES THEREBY FILLING SAID HOLES, SAID RESISTANT FILM PREVENTING ADHENSION OF SAID FUSIBLE MATERIAL TO SAID METALLIC STRIP BEYOND SAID HOLES, SAID FILLED HOLES THEREBY CONSTITUTING SAID FUSIBLE SAFETY PLUGS. 